Fluoration of aliphatic halides



Patented Sept. 3, 1935 PATENT OFFICE FLUORATION OF ALIPHATIC HALIDES Albert L. Henne, Columbus,` Ohio, assignor, by

mesne assignments, to General Motors Corporation, a corporation of Delaware Application June 26, 1931, Serial No. 547,159 Renewed May 19, 1934 s claims. (ci. 26o- 162) This invention relates to the manufacture of fluoro and/or halo-uoro derivatives of aliphatic hydrocarbons by uoration of aliphatic halides with fluorine.

The objects of my present invention are to pro- `vide a process or processes for the uoration of the halo derivative or derivatives of aliphatic hydrocarbons by the use of iiuorine as the fluorating agent, either with or Without the aid of a catalytic agent, and more particularly to provide a process or processes for fluorating derivatives of aliphatic hydrocarbons byV permitting fluorine to contact with or to pass through the halogen derivative of the hydrocarbon.

f lFor illustrative purposes, I have disclosed apparatus for carrying'out my improved process, in which Fig. l' is a` diagrammatic View 1o1 an apparatus for producing th'eYhalo-'uoro derivatives; and l FigLfZ is a diagrammatic vievvfcfA one type of apparai'ius that may' Abe used `for'the'l'production of uorine. ,Y f In carryingjout my invention, theuse of y a catalytic agent is optional. vIt is preferred,be-v

cause it` rendersv the control of the iiuoration easier. If it is to 'be usedthen the reactionv chamber 2 0 may be supplied with the .catalytic agentl through'the opening 22. AThis catalytic agent may be such a compound as antimony pentachloride, antimony trichloride, or titanium tetrachloride. An aliphatic hydrocarbon derivative is pumped from the tank 36 by the pump 2| shown diagrammatically as driven by the motor 2|a, into the reaction vchamber 20, while the fluorine is fed intol thev reaction chamber 20 through the conduit 50 under the control of the valve 5I. 'I'he gaseous reaction products are separated in column. 23 and dephlegmator 24. The insufflciently iiuorated compounds are returned to the fluorating .zone while the sufficiently fluorated cbmpounds are discharged from the top of the dephlegmator and delivered to the washers 25 andv 26 and the dryer 21.` The temperature of the dephlegmator is adjusted in accordance with the pressure underwhich the reaction takes place so that this combination of temperature and pressure approximates-the vapor pressure characteristics of the desired product. The residue may be removed from the reaction chamber 2U through .the covered opening 22a.

'As a specific example, dichlorodifluoromethana is obtained from carbon tetrachloride, CCl4, by

uoration'. The CCli is introduced from the sup-t ply chamber36 intothe reaction chamber 20,"v

where'it mixes with .antimony pentachloride, if

a catalyst is to be used. The uorine enters the reaction chamber 20 through the conduit 50, and passes through the carbon tetrachloride. In this specific case room temperature is suilicient. The gaseous reaction products rise through the fractionating column 23 and the dephlegmator 24. 'Ivhe dephlegmator temperature is maintained at about 60 F., and the pressure is maintained at about 1 atmosphere. Under these conditions I have found that dichlorodifluoromethane, m CC12F2, is obtained from the top of the dephlegmator. The dephlegmator and the column return to the reaction chamber the partially iiuorated compound, monoiluorotrichloromethane, CClaF, and any unacted upon carbon tetrachloride, for further luoration tothe desired derivative, CClzFz. Y

Although specific temperatures and pressures have been given, it should be understood that Y these conditions may be varied to approximate 20 the vapor-pressure characteristics of the compound tobe made. The desired pressure in the system is obtained by regulating the discharge of thefinished product by manual 'control or by an automatic control discharge valve 32a. The 25 washer is provided with a supply of dilute aqueous solution of caustic soda from the supply chamber 29, while the Washer 26 is provided with a caustic soda solution from the chamber 3U. One of. these washers may be usedto remove 30 the chlorine gas from the CClzFz. The dryer 21 contains concentrated sulphuric acid supplied theretofrom the supply chamber 3 I. Upon leaving the dryer 21, the gases may passthrough the condenser 32, which may be cooled to a degreesuilcient to liquefy the gas, 25 F. or lower, at atmospheric pressure. The liquefied gas is then discharged from the condenser and collected in the flask' or bottle 33. A relief diaphragm 36 and pressure gauge 35 are provided. 40

While I have described a method of manufacturing dischlorodiiluoromethane from carbon tetrachloride, it should be understood that the same final product may be vobtained by the iiuoration of an intermediate fluorine compound such as CClaF.

Halo-fiuoro derivatives of other hydrocarbons than methane can be obtained. A chlorine derivative of ethane is introduced into the reaction chamber 2l) and by contact with the uorine 50 entering the reaction chamber, iluoration takes place. By controlling temperature and pressure in the fractionating column 23 and the dephlegmator 2l, the desired halo-fluoro derivative of the ethane is obtained. 65.

As specic examples of the ethane derivatives, trichlorotrifluoroethane, CzClaFs, is obtained by passing fluorine through a solution of hexachloroethane in difiuorotetrachloroethane. The reaction chamber, as well as the dephlegmator, is maintained at a temperature of approximately 90 F. The operation is carried out at a vacuum of approximately six pounds.

By passing luorine gas through a solution of hexachloroethane in difluorotetrachloroethane at substantially room temperature and with the dephlegmator maintained at substantially 60 F. tetrailuorodichloroethane is obtained. The operating pressure is about 1 atmosphere.

In all the specific examples set forth above, the fiuorine may be obtained in any known or desired manner. .Howeven for purposes of convenience, the fluorine may be manufactured from an apparatus substantially as that shown in Fig. 2, and may be fed directly to the reaction chamber 20. In this apparatus there is shown a tank |00, made preferably of Monel metal and heated by means of an electric resistance lui, the resistance |0| being spaced from tank |00 by means of vertical strips of insulating material Illia. A carbon electrode |02 extends downwardly through an insulator plug |03 into a fused iiuoride which may be KEHF, the plug |03 being carried by the bell |04, having its lower end perforated as at |04a. The carbon electrode constitutes the anode, while the metal container |00 constitutes the cathode, the anode and the cathode being connected into an electric circuit. The passage of electric current through the fused fluoride will cause electrolysis, wherein fluorine will be liberated and collected at the anode. 'This fluorine will pass through the delivery tube |08 and is fed directly to the conduit 50 and to the reaction chamber 20.

While I have disclosed specific examples illustrating my process, it should be understood that generically my invention relates to the manufacture of halo-fluoro derivatives of aliphatic hydrocarbons from halogen derivatives of such hydrocarbons by replacing one or more halogen atoms with fluorine by interacting a halogen derivative of an aliphatic hydrocarbon and fluorine, either with or without the aid of a catalyst. Further, while special conditions` under which the steps of the process-may be carried out have been indicated, it should be understood that these condltions are recommended conditions only.

\ In this application I have made numerous refaoiacsc erences to the control exercised in the specific examples because the literature statements covering sporadic attempts at uoration with iuorine are so incomplete and often misleading as to discourage the use of fluorine for this purpose. I have found adjustments of the operating conditions which control the process so that iiuorine may be used as a fluorating agent to obtain any desired product.

What is claimed is as follows:

1. The method of manufacturing a halo-nuoro derivative of an aliphatic hydrocarbon which consists in interacting in the presence of a pentavalent antimony compound a hydrocarbon derivative containing halogen other than uorine, with fluorine, replacing at least one halogen atom of the hydrocarbon derivative with fiuorine, v

driving oi the reaction products into a dephleg-v mator, condensing in the dephlegmator any insuniciently fluorating compounds, returning the insuicently uorated compound to be further `iuorated and withdrawing from the dephlegmator the suiciently uorated compounds.

2. The method of manufacturing a halo-nuoro derivative of methane which comprises interacting in the presence of a pentavalent antimonyl compounda derivative of methane containing a halogen other than fluorine, with fluorine, replacing at least one halogen atom other than uorine, with iiuorine, driving off thereaction products into a dephlegmator, condensing in the dephlegmatorl any insufc'iently iluorated compounds, returning the condensed insuiciently uorated compounds to be further interacted with fluorine and withdrawing from the dephlegmator the sufciently fluorated compounds.Y

3. The method of manufacturing a halo-uoro derivative of ethanevwhich comprises interacting in the presence of apentavalent antimony compound a derivative of ethane containing lhalogen other than uorine, with fluorine', replacing at least one halogen ato'm other than fluorine with iluorine, driving off thereaction products into a dephlegmator, condensing in the dephlegmator the insuiciently fluorated compounds, returning from the dephlegmator the condensed insuffi-A ciently fluorated compounds to be further interacted with fluorine and withdrawing from the dephlegmator the sufficiently uorated compounds. v ALBERT L. HENNE. 

